There are a number of devices which serve to detect the presence of water or other liquids. U.S. Pat. No. 4,227,190 discloses a water alarm for monitoring floor moisture. This uses a plurality of printed circuit sensor electrodes to detect the presence of moisture on a surface. If moisture is detected, a gating signal is created causing an alarm to issue a warning. U.S. Pat. No. 4,020,478 discloses a moisture detector wherein current flows between electrodes in response to the presence of moisture. U.S. Pat. No. 3,200,388 shows a water leakage alarm system for washing machines. Additionally, U.S. Pat. No. 2,127,538 is a signaling device for indicating the wetting of a bed or bed clothing by the occupant thereof. While all of the aforementioned patents provide a warning system to indicate the presence of a liquid, these inventions do not provide a positive action of preventing further leakage. As a result, these devices are not particularly useful for unattended liquid chromatography experiments.
Additional liquid sensing mechanisms are disclosed in U.S. Pat. Nos. 4,206,871 and 3,758,855. The former uses a vibration-sensing means to indicate leakage from a centrifuge. The latter shows a resistance controllable indicator wherein changes in electrical resistance caused by moisture contact results in variations in generated frequency.
Devices which shut off liquid flow upon the detection of moisture are also shown in the prior art. U.S. Pat. No. 4,297,686 relates to a resistant liquid detection and shut-off system providing protection from water damage. This device requires a resistive sensing circuit system. Furthermore, while this device uses a solenoid-operated water shut-off valve, it is not adaptable for the compressive closure of tubing. U.S. Pat. No. 3,874,403 describes a safety attachment for appliances subject to fluid leakage. This device employs a switch that includes a fluid responsive member to indicate the presence of liquid and to initiate the shut-off of fluid flow.
While the aforementioned patented devices may act to detect fluid spillage, they fail to preserve the effluent that is detected. In essence, these systems detect fluid spillage but fail to provide a means for preserving the fluid. Preservation of the spilled fluid can be important for the later continuation of the experiment. Essential data or sample can be omitted where the spilled fluid is removed or destroyed after detection. In addition, while the aforementioned patented devices may be useful in small experimental settings, they would not be particularly applicable to large-scale scientific or industrial liquid chromatography systems.